This invention relates generally to an improved clean room facility and to a novel method for constructing the clean room facility, and more specifically to an improved floor configuration for a clean room.
Clean rooms are used extensively in the electronics industry and in other industries in which a clean, substantially particle free environment is necessary during the design, fabrication, assembly, or testing of a product. Clean rooms are rated by the number of particles of a given standard size that are detected in a standard volume within the clean room. According to this rating system a “Class 10” clean room has only one-tenth the particle count of a “Class 100” clean room. Similarly, a “Class 1” clean room has only one-tenth the particle count of a “Class 10” clean room. The low particle count in a clean room is achieved by a large number of distributed air changes in the room. Air flows through the room, usually in a laminar fashion and usually downwardly from the ceiling to the floor or to vents located near the floor. The air changes wash the particulate matter from the room. Other things being equal, the greater the number of air changes, the lower the particle count in the room. For example, a “Class 1” clean room usually requires on the order of 450 or more air changes per hour.
Typically the air in a clean room enters the room through filters or vents located in the ceiling, passes through the room, washing over the contents of the room, and exits the room through openings or vents in a raised clean room floor to a plenum formed between the raised floor and the underlying structural floor of the building. The air is then recirculated and again passes through the ceiling filters and into the room.
Prior art clean rooms use a raised clean room floor. The raised and usually perforated clean room floor is supported on a pedestal or plurality of pedestals. The pedestals are usually specially constructed structures designed specifically for the equipment that is to be placed on the raised floor. The raised floor itself is usually inadequate to support the weight of the equipment. The necessary pedestal structures are often very expensive, sometimes having a cost equaling a large percentage of the total equipment cost.
Presently known clean rooms also utilize the raised floor to form the return air plenum and to provide facilities to the equipment. For example, power lines, chemical lines, exhausts, drains, and the like typically pass through the raised floor and extend under the raised floor to a facilities area.
In addition to the expense of the customized pedestals used to support a raised clean room floor, there are a number of other significant drawbacks to a raised floor configuration. Because the raised floor, by itself, is unable to support the weight of equipment that might be placed in the clean room, the raised floor also cannot support the weight of that equipment as it is being moved within the clean room. This results in the necessity for disassembling the raised floor when equipment is moved into a clean room or is moved about the clean room. The floor is disassembled, equipment is moved within the clean room, placed on the portion of the raised floor in substantially its final location, and then the remaining portion of the raised floor is reassembled. This activity compromises the cleanliness of the clean room every time a piece of equipment is moved into, out of, or about the clean room. In addition, any facilities lines that may be located under the portion of the raised floor that is removed will also be disturbed by the moving of equipment. Because of these difficulties, it is commonplace to build relatively small or compartmentalized clean rooms so that only a small area is contaminated by any moving process. This, of course, leads to disadvantages in terms of material flow because materials being processed must be moved into and out of these individual compartmentalized clean rooms.
Much of the processing that is done in the clean room requires a substantially vibration free environment as well as a particle free environment. The use of raised clean room floors is also thought by many to suppress vibrations caused by the equipment located in the clean room. Although the raised floor and the platform upon which the raised floor is supported may dampen vibrations propagated by the underlying structural floor, the underlying slab floors found in known clean rooms nonetheless tend to be a conduit for vibration.
Many industries require substantially vibration free operating environments in which to house vibration-sensitive instruments and tools, such as those used by the microelectronics, medical, optical, biopharmaceutical, and other high-technology sectors. In the semiconductor industry, for example, the use of increasingly smaller microelectronic structures, including line widths on the order of 0.1 microns, has resulted in a need for higher levels of vibration isolation for vibration-sensitive tools. In this regard, equipment manufacturers are increasingly incorporating vibration isolation technology into their instruments and tools in an attempt to address the vibration isolation problem.
The problem of vibration isolation is complicated by the fact that it is often difficult to identify with certainty and to prioritize the factors that impart vibration to vibration-sensitive equipment. For example, it has been observed that equipment operating in other buildings, automobile traffic in the vicinity of a manufacturing or measurement facility, and even people walking in adjacent rooms or adjacent floors in a building can influence the vibration profile within a vibration-sensitive environment such as a semiconductor fabrication facility. Moreover, the design of a building or other structure, the materials used during construction, and other architectural and structural factors also influence the extent to which vibrations may be dampened or even amplified in the context of a vibration-isolation environment.
In an attempt to quantify standards for acceptable levels of vibration isolation in various environments, generic vibration criterion (VC) curves have emerged as a useful analytical tool. For more background regarding such generic vibration criterion, see, e.g., Institute of Environmental Sciences, “Considerations in Clean Room Design,” IES-RP-CC012.1 (1993), hereby incorporated by reference. With momentary reference to FIG. 7, the vibration sensitivity of a facility, for example a clean room, may be determined by plotting vibration data for the facility on a VC Curve set. For example, an accelerometer may be used to detect vibration information (expressed as velocity data in FIG. 7) for a range of frequencies of interest. By analyzing the plotted vibration data against the backdrop of a family of predetermined standard VC Curves such as those shown in FIG. 7, that facility may be classified in terms of its vibration isolation profile. By way of brief example, if all of the data taken and plotted for a particular facility is bounded by the VC-A curve shown in FIG. 7, the facility may be deemed adequate for housing tools such as microbalances, optical balances, and other equipment with a relatively low degree of vibration sensitivity. If, on the other hand, all of the data for a particular facility is bounded by the VC-D curve, then that facility may be deemed suitable for the most demanding equipment including semiconductor fabrication equipment operating in the 0.3 micron line width regime. See, Colin G. Gordon, Generic Vibration Criteria for Vibration-Sensitive Equipment, International Society for Optical Engineering (SPIE) Conference on Current Developments in Vibration Control for Optomechanical Systems, Denver, Colo. (July 1999), the entire contents of which are hereby incorporated by this reference.
Inasmuch as concrete slab and other known floor configurations contribute to the problem of vibration isolation, a new floor configuration for use with vibration-sensitive equipment is thus needed which overcomes the shortcomings associated with known floor configurations.
In view of these and other problems with conventional clean room designs, it has been recognized that a need exists for a clean room that is less expensive to build and to operate than a raised floor clean room. There is also a need for a clean room that allows for non-intrusive clean room practices for facilitizing equipment located in the clean room. The need also exists for a clean room that does not require an expensive and customized pedestal for equipment, but rather allows the placement of equipment anywhere within a clean room. There is also a need for a clean room into which equipment can be moved and relocated without compromising the integrity of the clean room. A need also exists for a clean room that can be large in area and conveniently expandable in area.
There is also a need for a floor configuration for use with vibration-sensitive equipment which dampens vibrations to, from and among the vibration-sensitive equipment.